From both the human point of view and that of physical geography, the comarca has a clear division into two subcomarques. Extending north from the valley of the Fluvià, is Alta Garrotxa (Upper Garrotxa), while the southern part is sometimes called the comarca of Olot, after the capital city.

The Fluvià flows toward the Mediterranean, and has a relatively small flow of water (1.07 m³/s at Olot).

The high humidity of Garrotxa contrasts with the that of the neighboring comarques. Annual rainfall is over 1000 mm (about 40 inches). It is said that "Si no plou a Olot, no plou enlloc" ("if it's not raining in Olot, it is not raining anywhere."). Winter temperatures hover around freezing; in August, temperatures average 27.7 °C (about 80 °F). Thermal inversions are relatively common; Alta Garrotxa and Puigsacalm, particularly, have more of a mountain climate, with snowfall figuring more prominently.

Vegetation varies with the climate. Alta Garrotxa and the east part of the comarca have typically Mediterranean climate and vegetation; the rest has a sub-Mediterranean climate, tending toward an Atlantic climate in the most humid areas.

The populated areas are mostly located on the plain and hillsides of Olot. A field of lava covers most of the plain (some 25 km²), and lava flows continue down the valley of the Fluvià to Sant Jaume de Llierca. Another important sector is in the tectonic valley of the River Ser, at the foot of the faultline escarpment of the Corb and Finestres ranges, with the volcanoes of Santa Margarida and Croscat. Lava flowed down the valley, past Sallent de Santa Pau to the Gibert mill. A third group of volcanoes lies in the Llémena river valley and the stream of Adri.

Romanesque monastery of Sant Joan les Fonts

The field became active about 700,000 years ago,[1] with the last eruption occurring 11,500 years ago.[2][3] There appear to have been old eruptions around Olot, because one can find basaltboulders from the Pliocene era in the valley of the Fluvià.

In 1982, the Generalitat de Catalunya declared the zone comprising the valleys of the Fluvià and Ser and the upper part of the valleys of Aiguavella and Sant Iscle to be Natural Places of National Interest. They also declared most of the volcanic cones and the Fageda d'en Jordà (beech woods rooted in lava) to be Integral Geobotanical Reserves.

9.4% of the population are engaged in agriculture and primary production, 59.4% in industry and energy, and 31.2% in the service sectors. Agricultural land has been shrinking, but Garrotxa remains the leading producer of maize. The livestock sector is actually expanding, especially pigs and cattle.

Industry, centered around Olot, Sant Joan les Fonts, and Besalú, has been generally on the rise since 1940. The most important industries are textiles, especially knitwear, the processing of locally grown food, and metallurgy. Behind these come papermaking, chemistry, and plastics.